Indonesia is the fourth most populous nation in the world. Of its large population, the majority speak Indonesian, making it one of the most widely spoken languages in the world.

Most Indonesians, aside from speaking the national language, are often fluent in another regional language (examples include Javanese, Sundanese and Madurese), which are commonly used at home and within the local community. Most formal education, and nearly all national media and other forms of communication, are conducted in Indonesian. In East Timor, which was an Indonesian province from 1975 to 1999, Indonesian is recognised by the constitution as one of the two working languages (the other being English), alongside the official languages of Tetum and Portuguese.